In recent years, toners have been required to have smaller particle diameters and hot offset resistance for increasing quality of output images, to have low temperature fixing ability for energy saving, and to have heat resistant storage stability for the toners to be resistant to high-temperature, high-humidity conditions during storage and transportation after production. In particular, improvement in low temperature fixing ability is very important because power consumption in fixing occupies much of power consumption in an image forming step.
In order to attain high-level low temperature fixing ability, there is a proposed toner containing a resin including a crystalline polyester resin, and a release agent, where the resin and a wax are incompatible to each other to form a phase separation structure in a sea-island form (see, for example, PTL 1).
This technique can achieve the toner excellent in low temperature fixing ability and heat resistant storage stability, but the toner containing the crystalline polyester tends to have low charging.
In order to improve charging, the toner generally includes a charge controlling agent containing an ionic compound such as a complex and an ammonium salt. However, these ionic compounds are easily dissolved in water. Therefore, in a polymerizing method in which particles are formed in an aqueous medium, the charge controlling agent present on the surface of the toner is dissolved in the aqueous medium, and thus the toner excellent in charging ability cannot be obtained. The toner containing the layered inorganic compound can improve charging ability of the toner without the charge controlling agent dissolved in the aqueous medium. Moreover, there is a proposed method for improving charging ability by modifying a part of materials present between layers of the layered inorganic compound to unevenly distribute the layered compounds on the surface of the toner (see, for example, PTL 2). Moreover, there is another proposed method for improving charging ability by binding a compound having a polar group such as fluorine onto the surface of the toner (see, for example, PTL 3).